1. Field of the Invention
The field of art to which this invention relates is structural elements, and more particularly to lightweight structural elements having a cavity in which a non-compressible material is disposed resulting in a rigid structure and/or one capable of vibration damping.
2. Description of the Related Art
It is highly desirable to build high speed machinery which are very accurate with structural elements that are light weight, have a high degree of stiffness, and have high internal damping characteristics. This is in fact the case for any product that is subjected to internally and/or externally induced vibrational excitation. With such structural elements, one can then design machines, structures, and other similar devices that are very accurate, that are lighter, and that can operate at higher speeds. This leads to a significant increase in performance.
In the prior art, when vibration becomes a factor, designers had the option of either adding various combinations of mass and viscoelastic material to the structure to employ a passive damper or employ some type of active damping device, such as a piezoelectric device. While the prior art passive damping devices have their advantages, they suffer from the disadvantage of greatly increasing the weight of the structure. This results in a reduction in the attainable speed of the machine or device. Active dampers, on the other hand, are usually lighter but greatly increase the cost of the machine as well as the cost of its operation.
For the above reasons, there is a need in the art for a low weight, low cost structural element that is very rigid and has high internal damping.
Therefore, it is an object of the present invention to provide a light weight structural element.
It is a further object of the present invention to provide a low cost structural element.
It is yet a further object of the present invention to provide a light weight structural element that provides for increased rigidity over comparable weight structural elements.
It is still yet a further object of the present invention to provide a structural element that is light weight and has high internal damping.
Accordingly, structural elements are disclosed, wherein a first embodiment has an enclosure having walls surrounding a cavity, and a non-compressible material disposed in the cavity. The walls are shaped such that a force tending to compress the element by a first deflection causes an amplified second deflection of the walls into the non-compressible material. The second deflection exerts a compressive force against the non-compressible material, resulting in a resistance to the first deflection and the force tending to compress the element.
In a second embodiment, the structural element has an enclosure having walls surrounding a cavity, and a non-compressible material disposed in the cavity. The walls are shaped such that a force tending to elongate the element by a first deflection causes an amplified second deflection of the walls into the non-compressible material. The second deflection exerts a compressive force against the non-compressible material, resulting in a resistance to the first deflection and the force tending to elongate the element.
In a third embodiment, the structural elements of the first and second embodiments are combined where a first enclosure having first walls surrounding a first cavity is provided. A second enclosure having second walls surrounding a second cavity is also provided. The structural element further has a first non-compressible material disposed in the first cavity, and a second non-compressible material disposed in the second cavity. The first walls are shaped such that a first force tending to compress the element by a first deflection causes an amplified second deflection of the first walls into the first non-compressible material, exerting a first compressive force against the first non-compressible material, resulting in a resistance to the first deflection and the first force tending to compress the element. The second walls are shaped such that a second force tending to elongate the element by a third deflection causes an amplified fourth deflection of the second walls into the second non-compressible material, exerting a second compressive force against the second non-compressible material, resulting in a resistance to the third deflection and the second force tending to elongate the element.
In a fourth embodiment of the present invention the structural element of the first embodiment is configured into a cylindrical enclosure having a wall, a top, a bottom, and a cavity defined by the wall, top and bottom, the top and bottom being separated by a height. The structural element further having a non-compressible material disposed in the cavity. The wall is concavely shaped such that a first compressive force tending to decrease the height causes an amplified deflection of the wall into the non-compressible material, exerting a second compressive force against the non-compressible material, resulting in a resistance to the amplified deflection and the first compressive force.
In a fifth embodiment of the present invention the structural element of the second embodiment is configured similarly to the fourth embodiment except that the wall is convexly shaped such that a tensile force tending to increase the height of the structural element causes an amplified deflection of the wall into the non-compressible material, exerting a compressive force against the non-compressible material, resulting in a resistance to the amplified deflection and the tensile force.
In variations of the fourth and fifth embodiments, the wall comprises a plurality of panels, the panels being separated by a flectural joint for aiding the deflection of the wall into the non-compressible material.
In variations of the above embodiments, the structural elements are configured for either optimum damping or optimum rigidity or a combination of rigidity and damping.
In yet other variations of the above embodiments, the structural elements are disposed on, or in, structural beams configured for either optimum damping, optimum rigidity, or a combination of rigidity and damping.
In yet other variations of the above embodiments, the structural elements are disposed on, or in, motion impartation devices configured for either optimum damping, optimum rigidity, or a combination of rigidity and damping.
Another aspect of the present invention are methods of fabricating the structural beam embodiments of the present invention.